1. Technical Field
The present invention relates to a lens module, and more particularly, to a lens driving module with a compact structure.
2. Description of Related Art
In recent years, camera modules have been widely applied to various devices, and more particularly to mobile devices. Many mobile devices are even equipped with more than two camera modules, such as webcam and imaging lens, to meet consumers' different needs.
However, under the circumstance that the size of mobile devices has been gradually diminished, the integration of common components is becoming a challenging task. For example, the front and rear lenses of a mobile device are integrated to save the interior space of the device and to enable the mobile device to take photos from different directions. FIG. 1A is a perspective view showing a prior art mirror switch module 1, which can be received in an electronic device (not shown) and, together with the viewfinder of the electronic device, forms at least one imaging channel. The mirror switch module 1 comprises an actuator 11, a mirror 12 and a lens driving device 13. The actuator 11 is a rotary motor which performs the rotation operation via an electromagnetically switching valve, a rotor motor or a stepping motor. The rotation of the actuator 11 causes a rotary shaft 111 to rotate which, in turn, causes the pivotal rotation of a mirror supporting base 112. The mirror 12 is fixed to one side of the mirror supporting base 112 and can pivotally swing and be positioned at a first position or a second position (the positioning can be effected by a mechanical stop end). The lens driving device 13 has a lens 131 for imaging and an image capturing sensor (not shown) which provides the lens driving device 13 with an optical axis. The prior art mirror switch module 1 can change the extension direction of the optical axis by optionally switching the mirror 12 to the first position and the second position so as to form imaging channels in two different directions.
FIG. 1B is a schematic view showing the relation between the image capturing sensor 132 to the lens 131 in the prior art lens driving device 13 with respect to size. As most of the existing display devices display images on a 4:3 or 16:9 aspect ratio, the image capturing sensor 132 should be configured to have the same aspect ratio. As can be seen from FIG. 1B, the prior art lens 131 is circular, thus the base surface of the prior art lens driving device 13 is square and the image capturing sensor 132 needs to be fully covered by the optically effective area of the lens 131. Accordingly, the regions between the boundary of the image capturing sensor 132 and the lens 131 are substantially non-imaging regions which occupy a predominant proportion of the thickness of the mirror switch module 1. In other words, the thickness of the prior art mirror switch module should be subject to the diameter of the lens so that the thickness of the electronic device using the prior art mirror switch module is also subject to the diameter of the lens.
In order to further reduce the thickness of the electronic device, the arrangement of the lens and its peripheral mechanisms in the lens module is one of the problems to be solved.